contrib/examples/git-merge.sh: use the $( ... ) construct for command substitution

The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
	perl -i -pe 'BEGIN{undef $/;} s/`(.+?)`/\$(\1)/smg'  "${_f}"
done

and then carefully proof-read.
Signed-off-by: NElia Pinto <gitter.spiros@gmail.com>
Reviewed-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/examples/git-merge.sh

@@ -523,10 +523,10 @@ do
 
 	if test "$exit" -eq 1
 	then
-	    cnt=`{
+	    cnt=$({
 		git diff-files --name-only
 		git ls-files --unmerged
-	    } | wc -l`
+	    } | wc -l)
 	    if test $best_cnt -le 0 || test $cnt -le $best_cnt
 	    then
 		best_strategy=$strategy